Drug & supplement interaction

Thuja + Chloroquine

Chloroquine brand names: Aralen Phosphate, Aralen Phosphate Injection, Aralen HCL, Avloclor, Malarivon, and others.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Thuja has a moderate interaction with Chloroquine. Thuja products can contains significant amounts of thujone, a neurotoxin.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Thuja and Chloroquine

Here is the interaction we found between these two, with the evidence behind it.

Moderate

SEIZURE THRESHOLD LOWERING DRUGS

Why this applies to Chloroquine

Chloroquine falls under SEIZURE THRESHOLD LOWERING DRUGS — the group Thuja interacts with.

Thuja products can contains significant amounts of thujone, a neurotoxin. Theoretically, patients taking drugs that lower the seizure threshold might be at greater risk of seizure if they also take thuja. Advise patients taking these drugs to avoid thuja products. Some drugs that lower the seizure threshold include anesthetics (propofol, others), antiarrhythmics (mexiletine), antibiotics (amphotericin, penicillin, cephalosporins, imipenem), antidepressants (bupropion, others), antihistamines (cyproheptadine, others), immunosuppressants (cyclosporine), narcotics (fentanyl, others), stimulants (methylphenidate), theophylline, and others.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the thing to know about combining thuja with chloroquine. Concentrated thuja products can contain thujone, a compound that, in larger amounts, can act as a neurotoxin and make seizures more likely. Chloroquine itself is one of those medicines that can lower the seizure threshold, meaning it can slightly raise the odds of a seizure in people who are prone to them. Stack the two together and, at least in theory, you could be nudging that risk up a bit further.

I want to be honest about how strong this concern is. It's based on anecdotal reasoning rather than solid studies, so it's more of a caution than a proven danger. Still, since chloroquine already carries its own seizure and nervous-system effects, I'd steer clear of concentrated thuja while taking it. Please run it by your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Millet Y, Jouglard J, Steinmetz MD, et al. Toxicity of some essential plant oils. Clinical and experimental study. Clin Toxicol 1981;18:1485-98. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Thuja Also Interacts With Other Medications

Thuja has 575 moderate known drug interactions in our database — the Chloroquine one above is one of them. If you take anything else, check it against the full list below.

Moderate 575 No known interaction 2,255 (incl. Chloroquine)
Taking anything else?

Check Another of Your Medications Against Thuja

Covers the 2,830 medications we’ve checked against Thuja. Pick one to open its full report.

From our Q&A

Questions About Thuja or Chloroquine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Thuja or Chloroquine, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Chloroquine

This page covers Thuja only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Chloroquine page lists 29 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Hibiscus Sabdariffa (major), Biofeedback (moderate), Coffee Charcoal (moderate) and Dendrobium (moderate).

By severity: 2 major · 18 moderate · 9 minor.

From our pharmacist’s overview on the Chloroquine page

“Chloroquine treats and prevents malaria, and that is precisely why its interaction list earns genuine caution, because if a supplement keeps the drug from being fully absorbed, the infection itself can win. Of the 29 supplements and herbs on file, the dominant theme is reduced absorption, and both major-rated entries, activated charcoa…”

Reviewed by 2 · Jul 18, 2026

Open the Chloroquine interaction page

One more smart check

Taking Thuja as Part of a Dietary Supplement Product? Check It for Interactions

We hold 84 real supplement products containing Thuja, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Thuja. Your product may carry other ingredients that interact with Chloroquine too, on top of Thuja — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Thuja and Chloroquine Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Thuja
Top half

#534 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Chloroquine
Steady interest

#2,065 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Thuja

What is Thuja?

  • Warts and skin growths
  • Respiratory and immune support
  • Cold and upper respiratory symptoms
  • Topical skin conditions
  • Traditional use as a diuretic or to bring on menstruation

Thuja, also called northern white cedar or arborvitae, is a tree whose leaf and oil have a long history in folk and homeopathic medicine, especially for warts and immune support. Solid human evidence for these uses is very limited, and the undiluted oil contains thujone, which can be toxic. Talk with a pharmacist or doctor before using it, and avoid it during pregnancy and breastfeeding.

Read the full Thuja monograph & all interactions
Medication

About Chloroquine

What Is Chloroquine Used For?

Brand names: Aralen Phosphate, Aralen Phosphate Injection, Aralen HCL, Avloclor, Malarivon, Nivaquine

Chloroquine Phosphate tablets are used to treat uncomplicated malaria caused by susceptible strains of P. falciparum, P. malariae, P. ovale, and P. vivax. They are also used to prevent malaria when traveling to areas where chloroquine-resistant strains are not present.

Chloroquine Phosphate tablets are also approved for extraintestinal amebiasis — an infection with Entamoeba histolytica that has spread outside the intestines, such as to the liver. Important limitations apply: these tablets are not for complicated malaria, not for use in regions where chloroquine resistance is widespread, and they do not prevent malaria relapses caused by P. vivax or P. ovale without an additional medicine.

See full Chloroquine drug information
Keep checking

Other Drugs & Thuja

Browse every other medication we’ve checked against Thuja — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
575Moderate
0Minor
2,254No known interaction
575 Moderate 2,254 No interaction
Moderate

575 interactions

Showing 60 of 575 moderate interactions — see all 575 on the Thuja page.

No interaction 2,254 drugs checked — show the list

We also checked Thuja against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,254 medications checked with no known interaction — see the full Thuja list.

See the full Thuja interactions page
See every supplement checked against Chloroquine, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Thuja monograph › Uses, safety, and every drug interaction in one place Chloroquine supplement interactions › Every supplement checked against Chloroquine, ranked by severity Chloroquine drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Thuja and Chloroquine Together: Common Questions

Can you take Thuja with Chloroquine?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Thuja and Chloroquine interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Chloroquine and Thuja?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.